Matthew Fradd began looking at pornography when he was eight. He found a magazine in a relative’s shed and was “completely captivated” by it. He started rooting around his relative’s house for similar material, and by the age of 11 or 12 he and a friend were stealing magazines from local shops and petrol stations. They would pretend to look at car magazines or heavy metal magazines, and, when they thought no one was looking, would stuff a Playboy or Penthouse under their jumper and run out. Fradd ended up with quite a collection, all of it stashed away under his dresser.

It is a story he has told many times before – on television and on radio, and to crowds of people in Canada, Ireland and America. He does so because he believes that porn is not harmless, but evil, that it “cripples a person’s ability to love”. It emasculates men, he says, and degrades women.

When I speak to him he is in southern Australia, near Adelaide, visiting his parents. I can hear some banging in the background: his son is drumming saucepans. His wife, Cameron, is back home in Ottawa, Canada, along with their daughter.

The turning point in his life, he explains, was World Youth Day 2000 in Rome. Until then he had been a “self-declared agnostic” and had avoided going to Mass as much as possible. When the WYD offer came up, he was attracted by the adventure of travelling to Europe. “The idea of growing in my faith or discovering Jesus or listening to what the Pope had to say – I didn’t really give a stuff about that, to be honest,” he says.

He was struck, though, by the other teenagers on the plane. “I’d never met young Christians who really believed their faith, who lived out the Church’s teaching on everything including their sexuality. I’d never met people like that who were normal. And not just normal but very cool. And confident.”

He began to pray tentatively for a sign that God existed. Before long, it seemed like his prayer was being answered. “I’d never felt so joyful in my life,” he says. “I just had this overwhelming sensation that God is real, that He loves me, and if that’s true how much does that change everything.” The “slow process of sanctification”, he says, began then.

He received mixed advice on pornography from priests. Some, he says, told him it was “terrible preparation for marriage”; others said it was merely “healthy entertainment for young boys” (this, Fradd says, was really not satisfactory).

He started going for longer and longer periods without it. He joined Net Ministries in Canada, and went evangelising around the country for a year. And, in 2006, he got married.

At this time, he says, he “wasn’t really struggling a whole lot but occasionally”. Then he had a particularly bad fall. “While my wife was leading a Bible study with women, teaching women about their dignity, I was looking at pornography,” he says.

He felt “absolutely ashamed”, he says, and told his priest in Confession that he was “sick and tired” of repeating the same thing again and again. His priest suggested that he turn to Our Lady of Purity for help. Fradd didn’t really believe it would work, but thought he should try it anyway.

“From that day on I took up the rosary and prayed for that intention,” he says. “And at the end of each rosary I would hold up the rosary above my head like a chain in two hands and say: ‘Blessed Mother, I have taken up your chain, now you take off my chains of lust.’ ”

Finally, he says, he “felt the addiction leave”.

But Fradd is wary about saying that he has overcome the problem for good.

“It didn’t happen overnight, and I’m not trying to say it could never happen again,” he says. Purity, he explains, is a daily battle. “It isn’t a destination that you reach and you wake up and think: ‘Oh, look at this, I’m pure.’ As a Christian, purity isn’t the destination; heaven is the destination.”

It was only a few months later that Fradd began to wonder how he could help other men and women struggling with the same problem. He recorded his testimony, and launched the “cheapest, poxiest website you’d ever seen”. And he started getting contacted by people all over the world.

In 2009 a priest gave him $12,000 to turn the site, ThePornEffect.com, into something polished and professional. Now it gets about 7,000 visitors a day, and has articles and interviews with people who have worked in the porn industry, including Donny Pauling, an ex-Playboy producer, and April Garris, an ex-porn star.

It also offers a forum, called “the Revolution”, for people who are trying to overcome their addiction, with “victory stories” from people who have managed to break the habit and a “battle cry” section from people in the midst of struggle. It is moving and extremely confessional: reading it feels like stumbling into an AA meeting.

Fradd says people should be honest and admit that churchgoers can be addicted to pornography, too. “Those who sit next to us at church may not believe there’s a problem with pornography, and maybe they do and they’re up to their eyeballs in it.”

On the phone, he says he forgets that other people aren’t as comfortable talking about pornography as he is. “It’s kind of the main thing I do now,” he says.

But he realises that the “evils of pornography” is not a subject likely to draw a big crowd unless it is handled carefully. “What we try not to do is say: ‘Everyone, come to the church hall, this man is going to talk about pornography.’ Oh, great. That sounds terrific.”

Instead, he says, he arranges events at bars or jazz clubs and pitches them as offering the “inside scoop” on the porn industry. He may, for instance, interview Garris or Pauling onstage. “Everyone can come into a cool environment, buy a pint and just listen to a conversation… It’s a way to evangelise the half-convinced.”

From his own experience struggling against pornography Fradd recommends fasting and Adoration of the Blessed Sacrament as well praying the rosary.

“If I can’t say no to that next slice of pizza or that next cup of coffee, how on earth will I say no to a temptation to look at pornography?”

He adds: “Prayer without fasting is like boxing with one hand tied behind your back, and fasting without prayer – well, we call that dieting.”

Fradd is a riveting, charismatic speaker, even on the phone. But he also seems quite sensible and down to earth: he is careful not to hold himself up as a model of virtue, and is scrupulously humble about his efforts.

Essentially, he says, the point is not about looking, or not looking, at pornography; it’s about trying to be holy.

“We want to be the kind of men that, when we’re dead, Satan throws a party. He says: ‘Thank God he has gone, he caused my kingdom too much damage.’ That’s the kind of man I want to be. And I think that’s the kind of man most men want to be.”